Acrylic rubber has the next highest heat resistance after fluororubber and silicone rubber, endures a high temperature of 150° C. or more and has resistance to lubrication oils such as engine oil and gear oil. Thus, it is used in the form of automotive molded products contacting lubrication oils under a high temperature atmosphere, such as, for example, a packing, a gasket, a sealing compound and a hose. A molded product using acrylic rubber is produced by injecting a mixture of acrylic rubber with various compounding ingredients such as a filler, an age resister, a processing aid and a crosslinking agent into a mold and subjecting the mixture to primary cure and then secondary cure. There is a cumbersome crosslinking step in the production process of a molded product of acrylic rubber.
In recent years, a thermoplastic elastomer produced without a vulcanization step and having moldability similar to that of a thermoplastic resin is being widely used as a material (raw material) alternative to a vulcanized rubber in automobile interior and exterior parts and in the electrical field. It has been attempted to substitute a thermoplastic elastomer for acrylic rubber. For example, the present applicant has proposed an olefin thermoplastic elastomer obtained by melt-kneading an acrylic resin, a graft copolymer comprising an olefin polymer segment and a vinyl polymer segment, a crosslinking agent, and a co-crosslinking agent (Patent document 1).
In addition, the following are known as conventional techniques for thermoplastic elastomer compositions: a thermoplastic elastomer composition comprising a thermoplastic polyester resin and a covalently-crosslinked acrylic rubber (Patent document 2); a thermoplastic elastomer composition produced by subjecting a mixture composed of 30 to 90% by weight of a thermoplastic copolyester elastomer and 70 to 10% by weight of an epoxy group-containing (meth)acrylate copolymer rubber to dynamic crosslinking using a polyvalent carboxylic acid compound (Patent document 3); and a thermoplastic elastomer composition comprising a thermoplastic ester polymer phase and a rubber phase containing a dynamically-crosslinked acrylic rubber (Patent document 4).
Patent document 1: Japanese Laid-Open Patent Publication No. 2004-002743
Patent document 2: Japanese Laid-Open Patent Publication No. 01-306447
Patent document 3: Japanese Laid-Open Patent Publication No. 05-025374
Patent document 4: Japanese Laid-Open Patent Publication No. 2000-034395